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Updated: The biggest exchange-traded fund tracking the shares of US financial stocks abruptly tumbled nearly 10 per cent on Wednesday morning before immediately recovering, in the biggest such move since the market turmoil in August 2015.

State Street’s $22bn Financial Select Sector SPDR fund (XLF) tumbled as much as 9.4 per cent 57 seconds after the opening bell to $20.91 as a result of an erroneous trade that was later canceled. It instantly snapped back to $23.27, according to Bloomberg data, slightly above the previous day’s close of $23.08.

The intra-day decline that has since been removed from the trading tape was the biggest since August 24, 2015, when the so-called XLF nose dived 21.7 per cent before stabilising as part of a broader bout of intense volatility.

“This was not a ‘flash crash.’ These trades were erroneously printed to the tape, did not occur on an exchange and were subsequently cancelled,” State Street said in a statement on Thursday. “There was no impact to the fund.”

The market tumult in August 2015 stoked concern from regulators about the rise in ETFs, and the potential risks they represent when their prices begin diverging from the underlying assets they track.

In the case of the XLF’s move on Wednesday, the underlying index that the ETF tracks never traded in the red, according to Bloomberg data. Meanwhile, none of the components listed in the index had losses as steep as the ETF.

Similar to the August event, the move also occurred right after the opening bell.